The present invention relates generally to integrated circuit (IC) designs, and more particularly to an engineering change order (ECO) cell for reducing leakage power of IC.
An IC includes a great number of electronic devices, cells and circuit modules for carrying out certain functions as required by design specifications. These devices, cells and circuit modules are typically constructed on a semiconductor substrate overlaid by a number of metal levels, at which conductive patterns are deployed as an interconnection network. Besides these normally functioning electronic components, the IC also has some spare or “dummy” cells that do not play an active role in the IC operation. While the spare cells may be designed to carry out certain functions, they are not connected to the normally functioning electronic components according to the original circuit design of the IC. Some of the spare cells can be selectively connected to the normally functioning electronic components, during the revising or rerouting process of the IC. This process is often referred to as an ECO, and the spare cells can be alternatively referred to as ECO cells.
The ECO cells occupy approximately five to ten percent of the total cell count in a typical IC. Conventionally, the ECO cells are coupled to a power supply and ground, even though they are not connected to other electronic components in the IC. As a result, a significant amount of power would leak through those ECO cells. For example, the ECO cells typically account for approximately ten to fifteen percent of leakage power of an IC manufactured using the 90 nm semiconductor processing technology. This power leakage problem becomes more severe when the semiconductor processing technology advances and the IC continues to shrink in size.
Thus, desirable in the art of IC design are ECO cells that can reduce the leakage power of IC.